Java

Use your favorite Java HTTP library, such as HTTP-Request, Unirest, Apache's HTTPClient, a.s.o.

Basic example with HTTP-Request

Follow the installation instructions on HTTP-Request's site.

Then you can try:

// demo class
public class Main {

    // method main(): application entry point
    public static void main (String[] args) {

        // your credentials
        String apiKey = "xxxxxx";
        String login = "test@test.com";
        String password = "pwd";

        // api uri in "sandbox" environment
        System.out.println("uri : "+uri);
        String uri = "https://sandbox.clicrdv.com/api/v1/groups/:group_id/fiches.json?apikey=xxxxxx";

        // GET request:
        //   - to "https://sandbox.clicrdv.com/api/v1/groups/:group_id/fiches.json?apikey=xxxxxx"
        //   - with basic auth
        //   - print response body to standard output
        HttpRequest.get(uri, true, "apikey", apiKey)
                   .basic(login, password)
                   .receive(System.out);
    }

}